Manipulation and Read-out of Spins in Quantum Dots

Manipulation and Read-out of Spins in Quantum Dots

Vink, I.T.

Vandersypen, L.M.K. (promotor)
Kouwenhoven, L.P. (promotor)

Applied Sciences

2008-11-12

Besides an electric charge, electrons also have a tiny magnetic moment, called spin. In a magnetic field, the spin has two possible orientations: 'spin-up' (parallel to the field) and 'spin-down' (anti-parallel to the field) and can therefore be used as a quantum bit, the computational unit of a quantum computer. For quantum computations, quantum bits must have long relaxation and coherence times. Furthermore, one needs to be able to manipulate and read out the quantum bits. The research in this thesis aims at developing a solid-state quantum bit using electron spins, confined in quantum dots. We perform single-shot read-out of electron spin states and observe long relaxation times. These measurements also reveal that lattice vibrations (phonons) play a dominant role in the spin relaxation process. To increase the spin read-out fidelity we introduce a novel approach to ultrafast charge detection: a high electron mobility transistor operated as a cryogenic pre-amplification stage. Another essential requirement is the ability to coherently manipulate the electron spin, which we achieve by generating an oscillating magnetic field close to the dot. We also use this electron spin resonance technique to indirectly control the surrounding nuclear spins. This electron-nuclear interaction might be used to prepare a nuclear spin environment where fluctuations are reduced.

quantum dots
electron spin
nuclear spin
quantum computing
quantum coherence

http://resolver.tudelft.nl/uuid:bb508caa-16b2-42a2-a631-ae9dd0f9915f

978-90-8593-043-3

Institutional Repository

doctoral thesis

(c) 2008 Vink, I.T.